Phosphatidylinositol 3-kinase (PI3K) is a family of lipid kinases that phosphorylate phosphatidylinositol at the 3′ position of the inositol ring. PI3K is comprised of several classes of genes, including Class IA, IB, II and III and some of these classes contain several isoforms (reviewed in Engelman et al., Nature Review Genetics 7:606-619 (2006)). Adding to the complexity of this family is the fact that PI3Ks function as heterodimers, comprising a catalytic domain and a regulatory domain. The PI3K family is structurally related to a larger group of lipid and serine/threonine protein kinases known as the phosphatidylinositol 3-kinase like kinases (PIKKs), which also includes DNA-PK, ATM, ATR, mTOR. TRRAP and SMG1.
Vacuolar Protein Sorting 34 (VPS34) is the sole Class III PI3K family member. VPS34 functions in the formation and trafficking of multiple intracellular vesicles, including vacuoles, endosomes, multivessicular bodies, lysosomes and autophagosomes (reviewed in Backer Biochem J 2008; Yan and Backer Biochem J 2007). VPS34 carries out these activities by phosphorylating PtdIns forming PtdIns3P, resulting in the recruitment and localization of a variety of FYVE and PX domain containing effector proteins that facilitate vesicular formation, elongation and movement. At a cellular level, inhibition of VPS34 results in defects in protein sorting and autophagy. Broadly defined, autophagy is a regulated process whereby cells catabolize subcellular components targeted for degradation by enclosing them in double-membrane vesicles which then fuse with lysosomes. Autophagy has been best characterized as occurring during times of nutrient deprivation, but also plays a role in normal cellular and tissue homeostasis and functions, including the development of multiple tissue types, the immune response, clearance of neuronal aggregates and tumor suppression. In addition to functioning in vesicle formation and movement, VPS34 may also participate in several signal transduction pathways (reviewed in Backer Biochem J 2008). Given that VPS34 plays an important role in many critical cellular processes including autophagy, inhibitors of VPS34 may have therapeutic application in a number of diseases, including but not limited to cancer, muscular disorders, neurodegeneration, inflammatory disease, infectious disease and other age related illnesses (reviewed in Shintani and Klionsky Science 2004; Kondo et al Nat Rev Cancer 2005; Delgato et al Immunol Rev 2009). Therefore, it would be beneficial to provide novel VPS34 inhibitors that possess good therapeutic properties, especially for the treatment of proliferative, inflammatory, or cardiovascular disorders.